1. Field of the Invention
The present invention relates generally to apparatus for absorbing kinetic energy and, more particularly, to apparatus for protecting circular or spherical structures from damage from collisions. The invention relates especially to passive apparatus for protecting the submarine-mating apparatus of a deep submergence recovery vehicle (DSRV) from damage as a result of a collision with solid objects. The invention further relates to shock absorbers and, especially to a passive sea water metering shock absorber employed in the apparatus for dissipating the collision forces.
2. Description of Prior Art
A primary purpose of the DSRV is to rescue the crew from a distressed submarine. Consequently, the DSRV has a spherical mating skirt which extends downward from the pressure hull of the DSRV (See FIG. 1) and which is intended to mate with the distressed submarine at the submarine's hatch to provide a passage from the submarine to the interior of the DSRV. The mating skirt has an O-ring seal at its mating surface which seals the submarine-mating skirt connection so that the interior of the mating skirt may be dewatered to allow personnel to pass between the submarine and the DSRV. It is most important to protect the mating skirt and, in particular the mating surface from damage as a result of collisions with undetected solid objects or accidental impacts during the mating process to insure that a satisfactory seal may be attained.
In the past, this mating surface has been protected by a shock mitigation system in which a shock mitigation ring is suspended from the lower ends of eight actively-controlled shock absorbers. The upper ends of the shock absorbers are fixed to four pylons which are attached to the outer hull primary structure. The shock absorbers which employ electrically controlled metering valves and fixed orifices to dissipate collision forces, are controlled from the DSRV and use the DSRV's hydraulic and electrical systems. This actively controlled system is not entirely satisfactory.
Primary among the disadvantages are the maintenance and reliability problems associated with the complicated nature of an actively-controlled system. These problems are compounded when the system must be exposed to the corrosive effects of sea water. In addition the complicated, actively-controlled system is very costly to build and maintain.